Application of ZigZag Decoding in Frameless ALOHA

Abstract

As ZigZag decoding (ZD) can resolve a collision between two packets, the combination of ZD and successive interference cancellation (SIC) is expected to provide a lower packet loss rate (PLR) and higher average throughput than the conventional frameless ALOHA. Therefore, in this paper, we considered applying ZD in frameless ALOHA. A straightforward implementation is first considered while deriving the exact theoretical expression for the PLR, and implementation results show higher PLR and lower throughput performance than in the conventional scheme. In addition, we propose a sophisticated implementation called enhanced ZigZag decodable frameless ALOHA (E-ZDFA), where the transmission probability is dynamically increased to improve the throughput by enhancing the chances for unretrieved users to transmit. The computer simulations revealed that E-ZDFA achieves higher throughput performance than the original frameless ALOHA and the state-of-the-art irregular-repetition-slotted ALOHA. Moreover, E-ZDFA achieves a lower error floor than frameless ALOHA, enabling the prevention of user silence, i.e., no transmission of the packet during the protocol.

Keywords

• Frameless ALOHA
• successive interference cancellation
• ZigZag decoding